Speaker
Description
The X-ray-emission of high-redshift galaxy clusters and compact nearby groups hosting bright, active galactic nuclei (AGN) can be misclassified as point source emission by the source detection algorithms due to the sizeable point-spread function of eROSITA.
In an analogous way to the treatment of the extended source catalog, we search for clusters in the eROSITA point source catalog. For this, we scan all positions of X-ray point sources with a high detection likelihood in the optical and near-infrared DESI Legacy Imaging Surveys data using the eROMaPPer algorithm. This procedure finds red-sequence galaxy overdensities at $\sim 16\,000$ locations after removing the lower richness ($\lambda \leq 16$) candidates and likely duplicates.
To characterize these sources, we additionally consider the optical and near-infrared counterparts to the X-ray point sources under the assumption that they are genuine point sources (e.g., AGN) identified via the NWAY algorithm, and compare the photometric cluster redshifts to the photometric redshifts of these single-source counterparts.
Of the $\sim14\,000$ point source cluster candidates with counterparts having sufficient photometry, we note that $\sim 11\,500$ are not yet listed in the literature.
We suspect that a high amount of genuine clusters in the higher redshift regime that would normally lie below the detection limit of eROSITA is found here because the X-ray emission of a coincident genuine point source along the line of sight boosts it.
In this talk/poster, I will present the properties of the clusters misclassified as point sources in the eROSITA X-ray catalog, and conclude by showcasing some of the most interesting candidates.
